Small internal combustion engines, such as those used in snowblowers, lawnmowers, generators, and the like are generally manually cranked through operation of a pull rope. In cold weather, oil thickens, slowing the cranking speed, and gasoline will not vaporize as readily. This results in the engine being more difficult to start in cold weather. Choking aids in cold weather starting but extensive choking can cause flooding and stalling of the engine.
To aid cold weather starting, priming systems have been utilized with internal combustion engines. In dry priming systems, pressurized air is injected through a manually operated primer pump into the fuel chamber, while in wet priming systems, fuel is injected directly into the cylinder. However, wet priming systems, as used in the past, have been relatively complex and expensive and in some cases have been tied in directly with the fuel pump.